The capacity of liver microsomes to form benzo[a]pyrene-diolepoxide-DNA adducts and induction of cytochrome P450 1A in feral fish exposed to pulp mill effluents.

An investigation was made of cytochrome P4501A (CYP1A) induction, determined by the activity of EROD (7-ethoxyresorufin O-deethylase), and formation of benzo[a]pyrene-diolepoxide-DNA (BPDE-DNA) adducts, measured by synchronous fluorescence spectrophotometry, in liver microsomes of perch (Perca fluviatilis), bream (Abramis brama), and roach (Rutilus rutilus). Fish were collected from the southern part of Lake Saimaa (Finland), an area polluted by effluents from the pulp and paper industry. In addition, two conjugation enzymes (UDP-glucuronosyltransferase and glutathione S-transferase) were determined. Overall, when compared to an upstream reference, EROD activity was higher in fish at waters downstream of the mill sewer. In bream EROD activity was threefold and in roach twofold. The changes in conjugation enzymes were not clearly related to the pollution gradient. The formation of BPDE-DNA adducts by liver microsomes was in correlation to both the pollution gradient and the EROD activity. This implies that CYP1A enzymes may play an important role in carcinogen activation in natural fish populations and that the formation capacity of DNA adducts may be a useful indicator when evaluating the potential toxicity of industrial water pollution.